INCOME TAXES - Schedule of Effective Income Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effective Income Tax Rate Reconciliation, Amount:
Provision at expected rate									$ 5,996	$ 6,260	$ 5,962
Decrease in tax resulting from:
Tax-exempt income									(1,492)	(1,673)	(1,933)
Tax credits									(737)	(737)	(737)
Other, net									(31)	(46)	159
Total provision	$ 1,106	$ 957	$ 825	$ 848	$ 652	$ 1,576	$ 875	$ 701	$ 3,736	$ 3,804	$ 3,451
Effective Income Tax Rate Reconciliation, Percent:
Provision at expected rate (as a percent)									34.00%	34.00%	34.00%
Decrease in tax resulting from:
Tax-exempt income (as a percent)									(8.46%)	(9.09%)	(11.02%)
Tax credits (as a percent)									(4.17%)	(4.00%)	(4.20%)
Other, net (as a percent)									(0.18%)	(0.25%)	0.90%
Effective income tax provision (benefit) and rate (as a percent)									21.19%	20.66%	19.68%